Running 5.3 executable on 5.2

I have a C++ executable that was compiled on AIX 5.3 but when I run on
AIX 5.2 get the following error.
I have updated the XL C/C++ runtime (xlC.rte) to the same level as on
5.3 but still get the error.
Any ideas?
exec(): 0509-036 Cannot load program myprogram because of the following
errors:
0509-130 Symbol resolution failed for myprogram because:
0509-136 Symbol __pth_init (number 100) is not exported from
dependent module /usr/lib/libpthreads.a(shr_xpg5.o).
0509-192 Examine .loader section symbols with the
'dump -Tv' command.